On New Year’s Day 2015, as celebratory fireworks erupted around the world, a quieter but no less explosive change was happening in Kiribati. After years of planning, the central-Pacific nation finally instigated a complete ban on all fishing within a 157,000-square-mile area of ocean, equivalent in size to California. This area—the Phoenix Islands Protected Area (PIPA)—had enjoyed limited (and controversial) protections since 2008. But the upgrade of 2015 turned it into one of the biggest protected areas on the planet, and arguably one of the most lauded. Here was a place where some 500 fish species could swim untroubled. Here was a sign of humanity’s growing commitment to protecting the oceans.

But the lead-up to this upgrade was a long one, full of the usual gauntlet of debates, public meeting, and blue-ribbon panels. Those discussions had been going on since at least the fall of 2013—and that gave fishers time to react. By analyzing ship movements, Grant McDermott from the University of Oregon and Kyle Meng from the University of California at Santa Barbara have shown that fishing intensity more than doubled in the site of the future reserve in the run-up to 2015. The damage was equivalent to fishing continuing for another year and a half after the ban took effect. The path to fully protecting PIPA triggered a preemptive race to yank as many fish from its waters as possible before the opportunity to do so closed for good.

McDermott, Meng, and their team describe this effect as a “blue paradox,” in which environmental policies that are meant to save the oceans create new incentives that worsen the problems they were designed to address—if only temporarily.

This is admittedly a study of a single marine reserve—an anecdote, albeit one grounded in very thorough data. “It needs to be replicated in other parts of the world,” says McDermott. “But I think PIPA makes a very good case study. It has been held up as a paragon of conservation success. It’s very large, and people have been trying to create more of these mega-reserves. We don’t want to be party poopers, but having demonstrated this effect in the paragon case, there should be a larger conversation about how you make the transition” to full protection.

Around 7 percent of the world’s oceans currently fall within marine protected areas, and some of these completely prohibit fishing, mining, and other extractive activities. These “no-take” regions are growing in both number and size, and if the International Union for Conservation of Nature (IUCN) has its way, they will encompass 30 percent of marine habitats by 2030. McDermott, Meng, and their colleagues calculate that if the world meets the IUCN’s target, preemptive harvests would lead to severe overfishing in about a third of global fishing areas.

But “the potential blue paradox is a small price to pay for a forever blue paradise,” says Randi Rotjan, the co-chief scientist of PIPA. The area is now in its fourth year of no-take status, which far exceeds the estimated 1.5 years it needed to compensate for the preemptive fishing. “Any possible short-term pain has been exceeded by long-term gain,” Rotjan adds.

Perhaps, says McDermott, but we can’t know that for sure. The 1.5-year estimate was based on the movements of fishing boats, and it doesn’t account for any effects on specific fish. Even a brief spate of extra fishing could potentially drive rare species past the tipping points where their populations can’t recover. “Or maybe you have some irreversible habitat damage when you go in all guns blazing,” says McDermott. That’s all speculation, but the point is, no one knows if the anticipatory fishing had any lasting harm.

Fortunately, scientists are now gathering the data that will allow them to address these questions. This new PIPA study, for example, was only possible because of an initiative called the Global Fishing Watch, led by the nonprofits Oceana and SkyTruth, and supported by Google. The program relies on an automatic tracking system whereby ships continuously transmit their position, speed, and identity to satellites. From the 20 million such records compiled every day, Google’s machine-learning tools can estimate how much fishing activity is happening at any place in the world.

The team used the Global Fishing Watch data to compare PIPA to the Line and Gilbert Islands, which were not included in the no-take zone. Both regions are part of Kiribati, both contain mostly the same fish as PIPA, and until August 2013, both were indistinguishable from PIPA in their levels of fishing. After that point, fishing pressure climbed in PIPA as awareness of a potential closure started to grow, and then fell to zero once that closure actually happened. No such changes befell the Line and Gilbert Islands.

“This effect hasn’t been studied or widely talked about, so it really adds a new dimension to how we need to think about marine reserves,” says Sarah Lester from Florida State University, who studies marine conservation and policy. These reserves are controversial, and some studies find that fish stocks don’t actually recover after protections are put in place. Perhaps the blue paradox is to blame. “Poor-performing marine reserves might be recovering from anticipatory fishing pressure, and will become high performers given more time,” says Lester.

This kind of preemptive effect has long been documented on land. When landowners in North Carolina realized that the red-cockaded woodpecker was about to gain protections under the Endangered Species Act, some of them responded by cutting down the pine trees that the bird nests in, so they wouldn’t be subject to any future restrictions.

But it wasn’t obvious that these examples of the so-called green paradox should have blue counterparts in the oceans. They happen because people have secure property rights over specific pieces of land, and are then forced by some policy to use it or lose it. No such secure rights exist in the seas; no particular boat owns any given stretch of water. The assumption was that “people are already in cutthroat competition, and everyone is already fishing as hard as they can,” says McDermott. “So where did this extra effort come from?” He and his team have a few ideas that they want to test, but the more pressing concern is this: Now that conservationists know about the blue paradox, is there any way to avoid it?

The obvious solution is to “reduce the time between announcement and enforcement,” says McDermott, but he recognizes that as recommendations go, that’s a somewhat glib one. These reserves don’t get established overnight, and they need support from many different entities if they’re going to work. That’s increasingly true since extremely large, PIPA-esque marine protected areas are in vogue, and these often require complex agreements between several governments and other parties.

“I wouldn’t make dramatic changes to how we plan or execute marine reserves until we know more,” says Lester. “Gun-control advocates would never suggest we should stop trying to pass gun-control measures because of the surge in gun purchases it triggers. It is important to be aware that the blue paradox could be happening. But this doesn’t suggest that we shouldn’t protect areas of the ocean from fishing, or that marine protected areas should be created in secret, or with much shorter public decision-making processes.”

“It would be a bummer to see this used as an excuse to shortcut public consultations,” says Ayana Elizabeth Johnson, a marine biologist who founded and runs the conservation consultancy Ocean Collectiv. “But it would be great to see this as a rationale for acting quickly on enforcement once a marine reserve is declared. It seems like there is often quite a long lag.”

“And more broadly, this is rationale for sustainable fishing regulations everywhere, to prevent overfishing even where there are no marine protected areas,” she adds.

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